Tar Shampoo advice

[KLBolton]

It's that time of year again when my psoriasis gets at its worst...

My scalp psoriasis is currently out of control I currently use Ketopine shampoo but it doesn't seem to be working at the minute if anything making it worse. I was just wondering people's views on tar shampoo and if someone could explain how the shampoos work, and any tips or advice on controlling the flakes although at the minute there more like bits. I have to tie my hair back to cover it but its not wlenoygh at the minute :(

Thanks Kath